Both rival groups blame each other for starting the clashes. A criminal investigation is now under way.

This follows Thursday night's violence in Donetsk, also in the east, where at least one person died in fighting between a pro-Russian crowd and supporters of the new government in Kiev.

Ukraine accuses Russia of using provocateurs to stoke unrest on the eastern border. Moscow denies this, vowing to protect its "compatriots" from far-right radicals.

'Consequences'

Earlier on Friday, US Secretary of State John Kerry and Russian Foreign Minister Sergei Lavrov failed to reach agreement on how to resolve the Ukraine crisis.

Media playback is unsupported on your device

Media captionRussian Foreign Minister Sergei Lavrov: "We will respect the will of [the] people of Crimea"

After six hours of talks in London, Mr Lavrov said both sides had "no common vision" on the issue.

However, he described the meeting as "constructive".

And Mr Lavrov stressed that Moscow would "respect the will of the people of Crimea".

Meanwhile, Mr Kerry, who described the talks as "direct and candid", said the US acknowledged Russia's "legitimate interests" in Ukraine.

But he stressed that Washington had not changed its position on the "illegitimate" referendum in Crimea and would not recognise its outcome.

He also said that his Russian counterpart had made it clear that President Vladimir Putin was not prepared to make any decision until after the vote.

And Mr Kerry added that he had told Mr Lavrov that there would be consequences if Russia "does not find a way to change course".

Both the US and EU have threatened tough sanctions against Moscow.

Russia's military intervention in the Crimean peninsula - part of Russia until 1954 and host to its Black Sea fleet - followed the fall of Ukraine's pro-Moscow President Viktor Yanukovych on 22 February.